Antenna



H. J. RIBLET Feb. 27 1951 ANTENNA 2 Sheets- Sheet 1 Flee Filed Nov. 6, 1945 INVENTOR. HENRY J. RI BLET A TTOR/VEY H. J. RIBLET Feb. 27, 1951 ANTENNA 2 Sheets-Sheet 2 Filed Nov. 6, 1945 INVENTOR. HENRY J. RIBLET' ATTORNEY Patented Feb. 27, 1951 ANTENNA Henry J. Riblet, Cambridge, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of War Application November 6, 1945, Serial No. 627,040

7 Claims.

This invention relates to antennas for communication systems and more particularly to an antenna for use as a beacon in connection with radio-object locating systems.

Heretofore it has been considered necessary, in order to obtain uniform omnidirectional radiation of energy, more particularly of horizontally polarized energy, that a beacon antenna be radially symmetrical in cross-section. It has now been found, according to this invention that substantially uniform omnidirectional radiation in a plane may be obtained with an antenna asymmetrical in cross-section such as of streamlined, tear-drop, or even of rectangular shape in crosssection. Such an antenna has several advantages, 1. e. when tear-drop or streamlined in shape, it avoids the necessity of a streamlined plastic housing which has a deleterious effect on the radiation patterns produced by known types of beacon antennas, it permits of several feed line for a plurality of antenna radiating arrays within the same structure and, as a separate array may be used for transmitting or receiving, a transmit-receive switch or box may be omitted. The latter advantage also applies to a rectangular antenna which has the additional advantage of permitting end-abutted antennas to be fed and which also avoids the necessity of matching rectangular waveguide feed lines to circular antenna elements.

It is an object of the present invention to provide a novel antenna which embodies the aforementioned advantages and overcomes the unsatisfactory features heretofore existing with radially symmetrical antennas.

It is another object of this invention to provide a beacon antenna having a streamlined, teardrop or other non-circular shape, including rectangular, in cross-section and which is capable of producing a substantially uniform omnidirectional radiation pattern in a plane perpendicular to the longitudinal axis of the antenna.

It is still another object of the invention to provide an antenna structure which is non-circular in cross-section and which is adapted to radiate horizontally polarized energy in a substantially uniform omnidirectional pattern in azimuth when in its contemplated vertical position.

For a better understanding of the invention together with other and further objects thereof, reference is had to the following description, taken in connection with the accompanying drawings, wherein like parts are designated by like reference numerals, and in which:

Fig. 1 is a horizontal sectional view of a rectangular hollow pipe antenna according to one embodiment of the invention.

Fig. 2 is a vertical side elevation of part of I the antenna accordin to the present invention.

Fig. 3 is a horizontal sectional view of another embodiment of the invention as applied to a streamlined or tear-drop shaped hollow-tube antenna.

Fig. 4 is a horizontal sectional view of a modification of the antenna of Fig. 3.

Figs. 5 and 6 are horizontal sectional views of still other modifications; and

Fig. 7 is a partly broken away perspective view of the antenna of Fig. 6.

Referring'now to Figs. 1 and 2 there is shown, by way of example, a beacon antenna I0 comprising a hollow pipe II of substantially rectangular cross-section which has its longitudinal axis vertical when the antenna is in its contemplated vertical operating position such as extending from the skin surface of an aircraft or other support. As shown, pipe I I is in the form of a wave guide and is of suitable dimensions to entertain the usual modes of energy wave propagation therein. Preferably for good radiation pattern distribution, the wider dimension b should be short relative to the wavelength of the energy in pipe II at the desired frequency of operation. Each of the opposite broad side walls I2 of pipe II are provided substantially centrally of the width thereof and approximately on the center line thereof, with a longitudinal vertical slot I3 of identical shape and dimensions. The slots may be approximately 3M4 long and their degree of narrowness may be determined to control to a certain extent the bandwidth of the antenna. The slots I3 are so excited that the emitted radiation from one slot I3 is preferably out of phase with its opposite slot. To aid radiation through slots I3. probes I4, which may be adjustable as to depth of penetration in pipe I0, may be located close to and approximately centrally of, either or both edges of each slot depending on the energy mode within pipe I0 and the phasin desired.

If desired a plurality of sections of pipe II may be mounted in aligned relation to form an array. In such an array arrangement, the slots I3 on each side of pipe II] are preferably aligned with their centers spaced apart by approximately one half of the wavelength of energy in the pipe I I and with their phase of excitation alternately reversed or they may be a full wavelength apart with no phase reversal. In the former case the slots l3 are preferably approximately M2 long. In either case, the adjacent aligned slots I3 of the array will radiate energy approximately in phase with each other but in opposite phase to the radiation from slots IS on the opposite side of pipe I I.

In Figs. 3, 4, 5 and 6 there are shown four modified forms of the invention in which the antenna id comprises a hollow pipe or tube Id of tear-drop shape (streamlined) in cross-section. The arrangement of the slots is similar to that described with reference to Fig. 1, the longitudinal axes of the slots !3 being approximately coincidental with the centerline of the two opposite sides [6. In Fig. 3 the probes I 4 are located in the same manner as in Fig. 1, that is on the same side of a plane through the longitudinal axes of slots 13.

The antenna of Fig. 4 is in the form of a coaxial conductor transmission line having a central conductor l7 located approximately along the axis of the spaced pipe Hi. The probes M in this modification are both on the far sides, or, as shown on the opposite sides of a plane through the longitudinal axes, of slots I3 assuming the current flow as indicated by the arrows. If desired pipe l5 may be filled with a dielectric material l5.

Fig. 5 shows a further modification in which the exciting energy is fed to antenna I B by means of a balanced two wire feed, the wires l8 and I9 thereof being of opposite polarity. Wires l8 and 89 are connected to opposite sides of slots l3 by means of connecting wires or rods 2!? and 2| respectively, the connections being reversed for one of the slots !3 to provide proper phase relationship.

In the modification illustrated in Figs. 6 and 7 the energy is fed to antenna it! by a coaxial conductor line 22 terminating in dipole sections 23 and 24, section 23 connecting the center conductor 25 with the edge of one of slots l3, while section 2 connects the outer conductor with edge of other opposite slot 13, these sections taking the place of the probes l-l, hereinbefore ed. The outer conductor 26 of line 22 is provided with diametrically opposed slots 2! extendin longitudinally from the end thereof for a distance of approximately we to provide impedance matching with the balanced dipole sections 23 and 26.

In Fig. 6 there is shown a partition 28 which extends longitudinally of member 55 substantially parallel to the plane through the slots i3. Such a partition may be included in all of the modified forms the invention and so position d as to provide proper internal dimensions of the member for proper modingof energy propagated therein.

While there has been described what is at present considered the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made herein without departing from the invention.

What is claimed is:

1. An antenna for radiating and receiving waves of electromagnetic energy in a substantially uniform omnidirectional energy pattern in a plane, comprising a tubular member of an electrically conducting material and of non-circular cross-section, the walls of said member on opposite sides of major axis of said cross-section each having a slot disposed longitudinally of said member, and means positioned in said member to cause propagation of electromagnetic energy therein in a mode with at least a component of the electric field across said slots in said crosssection and out of phase on opposite sides of said major axis.

2. An antenna as claimed in claim 1 wherein said member is a hollow pipe wave guide of rectangular cross-section and wherein said means comprises a probe extending inwardly from the edge portion of each slot at substantially midway of the length thereof, said probes being on the same side of a plane through the longitudinal axes of said slots.

3. An antenna as claimed in claim 1 wherein said member is a hollow wave guide having its cross-section substantially in the shape of a teardrop and wherein said means comprises a probe extending inwardly from the edge portion of each slot at substantially midway of the length thereof, said probes being on the same side of a plane through the longitudinal axes of said slots.

An antenna as claimed in claim 1 wherein said member is of streamlined shape in crosssection, in which a solid conductor extends longitudinally Within said member with its axis substantially coinciding with the longitudinal axis of said member, said member thereby comprising the outer conductor to form with said solid conductor a coaxial conductor transmission element for said energy and wherein said means comprises a probe extending inwardly from the edge portion of each said slot at substantially midway of the length thereof, said probes being on opposite side of a plane through the longitudinal axis of said slots.

5. An antenna as claimed in claim 1 wherein said member is of tear-drop shape in cross-section and includes a balanced two-wire conducting line extending longitudinally within said member for feeding energy to said member, and wherein said means comprises a conductor connecting one of said wires to one edge of each of said slots and a conductor connecting the other wire to the opposite edge of each slot, the connections to one of said slots being reversed with respect to the connections to the other slot.

6. An antenna as claimed in claim 1 wherein said member is of streamlined shape in cross-section and includes a coaxial conductor transmission line extending longitudinally within said member, the axis of said coaxial line substantially coinciding with the longitudinal axis of said member, and wherein said means comprises a dipole termination of said coaxial line, one of the sections of said dipole connecting the central conductor of said coaxial line to the edge portion of one of said slots, the other section of said dipole connecting the outer conductor of said coaxial line to the edge portion of the other slot, said connections to the edges of said slots being on the same side of a plane through the longitudinal axes of said slots.

7. An antenna for radiating energy in a substantially uniform omnidirectional radiation pattern in a plane comprising a hollow pipe ber of electricalh conductive material. said. her being of non-circular cross-section and ing a pair of broad walls on opposite sides of the major axis of said cross-section, each of said broad walls having a slot disposed longitudinally of said member and. substantially along the centerline of each of said broad walls whereby said slots are directly opposite each other, and means forcoupling each of said slots to energy propagated within said member whereby said mem- 5 slots are adapted to be excited by, and to radiate, said energy, said means being so positioned relative to said slots that the excitation of one of said slots is 180 out of phase with that of the other slot of said member.

HENRY J. RIBLET.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,129,669 Bowen July 9, 1940 2,238,770 Blumlein Apr. 15, 1941 Number Number Name Date Lindenblad July 22, 1941 Dallenbach Sept. 29, 1942 Dallenbach May 30, 1944 Southworth Feb. 20, 1945 Korman July 2, 1946 Lindenblad A Jan. 14, 1947 Wheeler Mar. 25, 1947 Johnson et a1 Dec. 30, 1947 Riblet Jan. 6, 1948 Bradley 1 May 24, 1949 FOREIGN PATENTS Country Date France May 8, 1939 

